Intraocular multifocal lens

ABSTRACT

An intraocular lens, in form of a disk, intended to replace the crystalline lens of a patient&#39;s eye, in particular after a cataract extraction, comprises on its distal side an aspherical sector extending approximately from the midline of the disk over one quarter of the surface thereof. The rest of the distal side is spherical. The radius of curvature of the aspherical sector varies monotonously between the value of the radius of the spherical sectors and a lower value. Such a configuration allows light rays impinging on the intraocular lens to be refracted at different angles and provides both near and distance vision. The discontinuity at transition between the aspherical sector and the spherical sector is blocked out by dark or etched plastic to eliminate glare. The proximal side can either be a convex surface, a concave surface or a plane.

PRIOR APPLICATION

This application is a continuation-in-part application of pending priorapplication Ser. No. 069,197 filed on July 2, 1987 for a IntraocularMultifocal lens, now abandoned.

FIELD OF THE INVENTION

The invention relates to aphakic lenses and more particularly to aphakicintraocular lenses.

BACKGROUND OF THE INVENTION

Intraocular lenses have been increasingly used in the last decade, inparticular in aphakic patients after a cataract operation. Intraocularlenses provide many advantages over both spectacle and contact lenses.They permit a better elimination of perceptual problems and reduce imagesize disparity. Since the intraocular lens is intended to remain insitu, it eradicates the difficulties in inserting and removing contactlenses encountered by elderly patients. The use of an intraocular lensmay also be advantageous for those working in unusual environments andfor those whose visual requirements for occupation must be fulfilled.Presently, opthamologists and eye surgeons recommend that intraocularimplant lens surgery be performed when the patient is not likely tomanage a contact lens.

According to Norman S. Jaffe et al, "Pseudophakos", published by TheC.V. Mosby Company, 1978, the majority of patients who undergo lensimplant surgery in the United States receive implants whose power isestimated from the basic refraction of the eye. Experience has shownhowever that there are many pitfalls in estimating the basic refractionin this way, in view of the high incidence of residual anisometropia andaniseikonia cases in patients thus corrected. More recentlyophthalmologists surgeons have endeavoured to design bifocal intraocularlenses (IOL hereinafter) to focus both the near and far images on theretina. The "Ocular Surgery News", June 1, 1987, Volume 5, Number 11,reports the latest findings concerning bifocal IOL's. These IOL's,however, provide near and distance vision but do not provide a continuumin the dioptric range. To the best of the inventor's knowledge, there isnot known any multifocal intraocular lens.

SUMMARY OF THE INVENTION

It is therefore an object of this invention to provide a new multifocalintraocular lens with a full dioptric range.

It is also another object of the present invention to produce anintraocular lens which can be easily and safely implanted in a patient'seye and which can provide optimal postoperative vision.

Another object is to provide an intraocular lens which can be easilymanufactured and can be produced at low cost.

Another object of the present invention is also to furnish anintraocular lens which is more particularly designed for the surgicalcorrection of aphakia following extracapsular cataract extraction.

In accordance with the present invention, an intraocular lens has thegeneral shape of a biconvex disk. The proximal side, to be placedagainst the vitreous humor is substantially spherical, whereas thedistal side is composed of three sectors. The upper sector isessentially spherical and extends to the midsection of the disk. Thecenter sector, adjacent the upper sector, extends therefrom to the lowerquarter of the disk and is formed of an aspherical sector of decreasingradius of curvature. The lower sector is also essentially spherical.Such a configuration allows light rays impinging on the intraocular lensto be refracted at different angles. The focal plane thus variescontinuously between a near focal plane for near objects and a far focalplane for distant objects, thereby permitting both near and far vision.The proximal side of the IOL can also be a plane or a concave surface inother embodiments of the present invention.

BRIEF DESCRIPTION OF THE DRAWING

Other objects and advantages of this invention will become more apparentfrom the following specification taken in conjunction with the drawingwherein:

FIG. 1 is a front perspective view from the distal side of anintraocular lens common to the first, second and third preferredembodiments of the invention;

FIG. 2 is a side view of a first preferred embodiment of the presentinvention;

FIG. 3 is a side view of a second preferred embodiment of the presentinvention;

FIG. 4 is a cross-sectional view of a third preferred embodiment of thepresent invention taken along line 4--4 of FIG. 1;

FIG. 5 is an optical diagram illustrative of the variable multifocaleffect achieved by the first preferred embodiment of the presentinvention.

FIG. 6 is a side view of the fourth embodiment wherein the asphericalsector extends over the entire central part of the lens;

FIG. 7 is a perspective view of the fifth embodiment which includes anupper spherical angular sector;

FIG. 8 is a cross-sectional view thereof taken along line 8--8 of FIG.7;

FIG. 9 is a side view of the sixth embodiment wherein the asphericity ofthe aspherical sector is achieved in discrete steps;

FIG. 10 is a perspective view of the seventh embodiment using concentricspherical and aspherical sectors;

FIG. 11 is a median cross-sectional view thereof; and

FIG. 12 is an optical diagram illustrative of the various multifocaleffects obtained with the seventh embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring now to FIG. 1, there is represented a front perspective viewfrom the distal side (or external side) of the intraocular lens of thepresent invention. The IOL of the present invention is particularlydesigned for the surgical correction of aphakia following extracapsularcataract extraction. This lenticulus is to be implanted in the posteriorchamber of the patient's eye and is designed to be placed in the ciliarysulcus.

As illustrated in FIG. 1, the IOL of the present invention has thegeneral shape of a biconvex disk. The distal side 1, represented in FIG.1, has a generally spherical form with the exception of a sector 3extending approximately from the mid-section of the distal side 1 to thelower quarter 4. The aspherical sector 3 is configured such that theradius of curvature decreases monotonously from the value R₁ of theradius of the upper spherical sector 2, to a lower value R₀. The lowerspherical sector 4 has the same radius as the upper spherical sector 3,namely R₀. Because R₀ and R₁ are different, the aspherical sector 3 andthe lower spherical sector 4 form an obtuse angle. R₀ varies typicallybetween 7 mm and 9 mm, whereas R₁ varies between 8 mm and 10 mm radiusof curvature in the preferred embodiments of the present invention. Thediscontinuity 5 between the aspherical sector 3 and the lower sphericalquarter 4 is blocked out by dark or etched plastic in order to eliminateglare. However, the transition may be so slight as to preclude the needfor any blocking or etching. The IOL is preferably made ofpolymethylmethacrylate (PMMA) or any other suitable material for IOL'ssuch as silicon or hydrogel. The asphericity of the sector 3 not onlyoccurs along the axis X of the intraocular lens, hereinafter referred asthe vertical axis, but also along the axis Z of the lens, hereinafterreferred as the horizontal axis. More particularly, the planes XY, XZand YZ are respectively called hereinafter the vertical plane, thedistal plane and the horizontal plane of the lens. The discontinuity 5therefore extends from the lower quarter 4 to the mid-section of thelens on the edges and has an annular shape, as shown in FIG. 1.

Now turning to FIG. 2, there is illustrated the first embodiment of thepresent invention in a side view. The proximal side 6 is a convexsurface in this embodiment. As illustrated in FIG. 1, the distal side 1shows the three sectors hereabove described, namely the upper sphericalsector 2, the central aspherical sector 3 and the lower sphericalquarter 4.

In FIGS. 3 and 4, there are illustrated two other embodiments of thepresent invention. In FIG. 3, the proximal side 7 is a plane, whereas inFIG. 4, the proximal side 8 is a concave surface. In each of theaforementioned embodiments, the distal side has the same configuration.

FIG. 5 is an explanatory optical diagram illustrating the multifocalproperty of the first preferred embodiment of the present invention asdescribed hereabove. It should be noted, however, that the opticaldiagram of FIG. 5 holds true for the other embodiments of the presentinvention. A ray of light A impinging upon the lens on its sphericalsector 2 is focused in the far focal plane, as indicated by FF. Theaspherical sector is tangentially adjacent to the spherical sector 2about the center of the mid-section of the IOL. As mentioned hereabove,the radius of curvature of the aspherical sector 3 varies from R₀, valueof the radius of the spherical sector 2, to R₁. A ray of light Cimpinging upon the bottom of the aspherical sector is thus focused in aplane FN2 located between the lens and the far focal plane by virtue ofelementary optical laws. The optic of the IOL of the present inventionprovides therefore both near vision through the aspherical sector 3 anddistance vision through the spherical sectors 2 and 4. Light B fromintermediate objects is also adequately focused in FN1 by the asphericalsector 3 because of its varying radius of curvature. The degree ofsphericity can be chosen to permit a full dioptric range, therebyproviding optimal post-operative vision. The principle underlying thefunctioning of the multifocal IOL herein disclosed, reposes on thegeneral concept that the brain selects one or the other of the imagesfocused on the retina by the IOL. This selection is based on differencesin contrast between the images perceived by the brain. Through each ofthe sectors of the IOL, the focused image and the unfocused images areprojected onto the retina, and the brain immediately selects the focusedimage. A loss of contrast is noticeable but not significant.

Now turning to FIG. 6, there is represented a side view of a fourthembodiment of the present invention wherein the aspherical sector 3extends approximately from the lower quarter 4 to the upper quarter 2.This aspherical sector 3 therefore defines two discontinuities 5a and 5bwhich can be both blocked out to eliminate glare as stated hereinbefore.

In the fifth embodiment illustrated FIGS. 7 and 8, the aspherical sector3 extends over the entirety of the central part of the intraocular lensas in FIG. 6 with the exception of an angular sector 9 in the upper partof the lens. More generally, the aspherical sector 9 can take variousshapes. The number of degrees of the aspherical sector in the plane ofthe lenticulus can vary from 180 degrees to 360 degrees as in FIG. 6 andcan take any intermediary value, as illustrated in FIG. 7. A valueinferior to 180 degrees is not excluded but may impair the near visionproperties of the intraocular lens.

Referring to FIG. 9, there is illustrated a sixth embodiment of thepresent invention similar to the first embodiment, but wherein theasphericity of the sector 3 is achieved in discrete steps. Theaspherical sector extends from the lower quarter 4 to the mid-section 2as in FIG. 2. However, the aspherical sector is constituted of threespherical domains 3a, 3b and 3c of decreasing value from R₀ to R₁. Itshould be understood that a greater number of discrete steps can beenvisaged. In the example illustrated in FIG. 9, the spherical sectors3a, 3b and 3c have respectively the following refractive powers: 1diopter, 2 diopters and 3 diopters. Such an arrangement allows to obtaina continuum of refractive powers. Because the asphericity of the sector3 extends both horizontally and vertically, the spherical sectors 3a, 3band 3c take the form of concentric cresents around the center of theintraocular lens in the distal plane thereof.

FIGS. 10 through 11 illustrates a seventh embodiment of the inventionusing concentric spheric and aspheric zones. More specifically theintermediary sector 13 is aspherical, while the central sector 12 andperipheral sector 14 are spherical. As in the previously describedembodiments, the radius of curvature of the aspherical sector 13decreases progressively as we get close to the peripheral sector 14.This embodiment of the invention is symmetrical about all meridians. Asthe diagram of FIG. 12 indicates, the most distant focal point 15corresponds to the spherical median and peripheral sectors 12 and 14,while the various proximal focal points 16, 17 correspond to thecontinuously variable aspherical sector 13.

It should be observed that minor variations of the aforedescribed IOLare envisageable, such as displacing upwards or downwards the threeconvex sectors hereabove described. In particular, the aspheric sectorcan be begin anywhere on the surface of the intraocular lens and be ofany radius. In the embodiments hereinbefore described, the asphericalsector has the same radius as the lens itself and therefore extends fromone edge of the lens to the other edge. A configuration wherein theaspherical sector occupies only the central part of the lens, ispossible and would serve the same purpose as the embodiment more fullydescribed hereabove. It should also be noted that the proximal side canbe otherwise configured.

While the preferred embodiments of the invention have been described,modifications can be made and other embodiments may be devised withinthe spirit of the invention and the scope of the appended claims.

What is claimed is:
 1. An intraocular implant to replace the crystallinelens of a patient's eye, in particular after a cataract extraction,comprising:a generally discoidal lens shaped to exhibit light convergingproperties over its entirety; said lens having a distal side and aproximal side to be placed against the vitreous humor of said patient'seye; one of said sides having a surface describing:a first sphericalsector; and a substantially aspherical sector tangentially adjacent tosaid first spherical sector, whereof the radius of curvature decreasesmonotonously from the value of the radius of said first spherical sectorat points of said aspherical sector nearest to the center of the lens,to a lower value at points of said aspherical sector farther away fromthe center of the lens; said decreases occurring along both the verticalaxis and the horizontal axis of the plane of said lens.
 2. Theintraocular implant of claim 1, wherein said first side is the distalside of the lens and said first spherical sector occupies the center ofsaid lens.
 3. The intraocular lens of claim 1, wherein said asphericalsector extends over the entire central part of said lens in the distalplane of said lens.
 4. The intraocular lens of claim 1, wherein saidaspherical sector extends over one half of the central part of said lensin the distal plane of said lens.
 5. The intraocular lens of claim 1,wherein the number of degrees of said aspherical sector measured in thedistal plane of said lens is between 180 degrees and 360 degrees.
 6. Theintraocular lens of claim 1, wherein said aspherical sectors isconstituted of a series of spherical sectors, whereof the radii ofcurvature decrease monotonously and discretely from the value of theradius of said first spherical sector to a lower value.
 7. Theintraocular lens of claim 1, wherein the radius of curvature of saidaspherical sector decreases continuously.
 8. The intraocular lens ofclaim 1, further comprising on its distal side a second spherical sectoradjacent to said aspherical sector and having the radius of curvature ofsaid first spherical sector.
 9. The intraocular implant of claim 8,wherein said first spherical sector extends substantially over one halfof said distal side in the vertical plane of said lens.
 10. Theintraocular implant of claim 9, wherein said aspherical sector extendssubstantially over one quarter of said distal side in the vertical planeof said lens.
 11. The intraocular implant of claim 8, wherein saiddiscontinuity is darkened.
 12. The intraocular implant of claim 8,wherein said discontinuity is etched.
 13. The intraocular implant ofclaim 1, wherein said lens is made of polymethylmethacrylate.
 14. Theintraocular lens of claim 7, wherein the radius of curvature of saidfirst and second spherical sectors is between 6 mm and 10 mm.
 15. Theintraocular implant of claim 1, wherein the radius of curvature in saidfirst spherical sector is between 8 mm and 10 mm, and said lower valueis between 7 and 9 mm.
 16. The intraocular implant of claim 1, whereinthe proximal side of the lens is a convex surface.
 17. The intraocularlens of claim 1, wherein said proximal side is a plane.
 18. Theintraocular lens of claim 1, wherein said proximal side is a concavesurface.
 19. The intraocular lens of claim 1, including a plurality ofconcentric aspherical and spherical sectors.